Non-magnetic noble alloy containing ruthenium, cobalt and chromium

ABSTRACT

A noble alloy suitable for dental purposes that contains cobalt and chromium in addition to ruthenium and optionally gold and/or platinum group elements, and is non-magnetic is provided. In the alloy system cobalt-chromium-ruthenium-gallium it was found that gallium contents above about 10 weight percent may exhibit ferromagnetism upon slow cooling. Ferromagnetism is an undesirable feature for dental prosthesis. Reducing the gallium content below 10%, however, lowers the thermal expansion coefficient of the alloy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/467,877, filed Mar. 25, 2011, the disclosure of which is incorporatedherein by reference.

FIELD OF THE INVENTION

This invention concerns a noble alloy suitable for dental purposes thatcontains cobalt and chromium in addition to ruthenium, and isnon-magnetic.

BACKGROUND OF THE INVENTION

Dental alloys employed in the porcelain-fused-to-metal processingtechnique may be classified into several groups: gold based; palladiumbased; cobalt based and nickel based. Typically, preferred alloycompositions have been tied to the cost of the alloy components. To thisend, the economic advantage of the cheaper base metals such as cobaltand nickel is obvious, but the functional characteristics of the basemetal alloys do not compare with those of the gold or palladium baseddental products. In general, the base metal alloys are more difficult tocast, grind and bond to porcelain.

There have been numerous attempts to improve the functionalcharacteristics of cobalt and nickel alloys through the addition of goldand the platinum group metals (the platinum group metals compriseplatinum, palladium, rhodium, iridium, osmium and ruthenium). ExemplaryUS patents describing such dental alloys include:

U.S. Patentee Pat. No. Comments Prosen 4,253,869 Describes a cobaltchromium alloy that may contain 7 to 15 wt. % ruthenium Prosen 4,255,190Describes a cobalt chromium alloy that may contain 1 to 5 wt. %ruthenium with gallium plus tungsten Zwingmann 4,382,909 Describes acobalt chromium alloy that may contain 1 to 70 wt. % palladium Prasad4,459,263 Describes a cobalt chromium alloy that may contain 5 to 15 wt.% ruthenium Vuilleme 6,613,275 Describes a cobalt chromium alloy thatmay contain 0.5 to 4 wt. % gold Prasad 6,656,420 Describes an alloy thatmay contain 25 to 60 wt. % gold and up to 2 wt. % ruthenium, the balancecobalt. Prasad 6,756,012 Describes a cobalt chromium alloy that maycontain up to 20 wt. % platinum or palladium, up to 10 wt. % gold and upto 6 wt. % ruthenium Cascone 7,794,652 Describes a cobalt chromiumalloys that contains at least 15 wt. % ruthenium, at least 40 wt. %cobalt and from 5 to 15 wt. % gallium

In each case, some improvement in the functional characteristics of thebase metal alloy is achieved through the addition of gold and theplatinum group metals. However, recently it has been discovered thatmany of these alloys have magnetic properties. In the past, suchmagnetic properties have not posed a significant problem. However, thegrowing importance of magnetically based imaging techniques has put theissue of dental appliances made from strongly ferromagnetic materials inthe spotlight, because the presence of such strongly ferromagneticmaterials in a patient can interfere with obtaining clear images fromsuch techniques.

One of the first attempts to describe a true “non-magnetic'” dentalalloy family was recently submitted by the assignee of the presentapplication, The Argen Corporation (U.S. Pat. Pub. No. 2008/0232998).Unfortunately, the alloys disclosed in this publication require the useof palladium, which is a relatively expensive noble metal. Accordingly,it would be desirable to find a similarly non-magnetic family of nobledental alloys comprising the less expensive noble materials, such as,for example, ruthenium.

SUMMARY OF THE INVENTION

Thus, there is provided in the practice of this invention according to apresently preferred embodiment, a workable noble alloy that isnon-magnetic and can be used in dental applications. The noble alloyaccording to the invention comprises: (i) at least 25 wt. % ruthenium;(ii) between 15-35% chromium; (iii) thermal and mechanical propertymodifiers selected from the group of Ga, Ge, Si, B, In, Sn, Al and RareEarths metals in amounts sufficient to result in an alloy that isnon-magnetic and having a lower, processable liquidus temperature(preferably below 1600 C.°, and more preferably below 1450 C.°; (iv) andthe balance cobalt.

In one such embodiment, the non-magnetic cobalt based dental alloyincludes:

-   -   at least 25 wt. % of Ru;    -   from 15 to 35 wt. % Cr;    -   from 30 to 50 wt. % Co; and    -   at least 5 wt. % Ga;    -   wherein where the concentration of Ga is from 5 to 10 wt. %, the        alloy further contains a sufficient concentration of up to 5 wt.        % of at least one modifier selected from the group consisting        Ge, Fe, B, In, Sn and Re such that the liquidus temperature of        the alloy is below 1600 C.°;    -   wherein where the concentration of Ga is greater than 10 wt. %,        the concentration of Co is at least 35 wt. %, the concentration        of Cr is less than 25 wt. %, and the alloy further contains B in        a concentration of up to 1 wt. %; and    -   wherein the alloy is non-magnetic.

In one such embodiment, the concentration of Ga is less than 10 wt. %and the concentration of Ru is from 25 to 45 wt. %, and the ratio of Coto Ga is 4 to 1 or less.

In another such embodiment, the concentration of Ga is less than 10 wt.%, and the alloy further contains at least 1 wt. % Re.

In still another such embodiment, the concentration of Ga is less than10 wt. % and the total concentration of Ga and Re is at least 10 wt. %.

In yet another such embodiment, the at least one modifier material isselected from the group consisting of up to 3 wt. % silicon, up to 1 wt.% boron, up to 3 wt. % aluminum, up to 3 wt. % germanium, and up to 1wt. % cerium.

In still yet another such embodiment, the alloy further comprises lessthan 5 wt. % of at least one trace additive selected from the groupconsisting of copper, nickel and iron.

In still yet another such embodiment, where the concentration of Ga isfrom 5 to 10 wt. %, the ratio of Co to Ga is greater than 4 to 1.

In still yet another such embodiment, the alloy is a compositionselected from the group consisting of Co₄₀Cr_(27.5)Ru₂₅Ga_(7.5),Co₃₈Cr₃₀Ru₂₅Ga₇, Co₄₁Cr₂₅Ru₂₅Ga₈Ge₁, Co₃₅Cr₂₅Ru₃₀Ga₁₀,Co₄₀Cr₂₅Ru₂₅Ga₅Re₅, and Co_(37.5)Cr₃₀Ru₂₅Ga₇B_(0.5). The suffixesrepresent weight % of the elements in the alloys and not atomicfractions.

In still yet another such embodiment, the alloy has a thermal expansioncoefficient within the range of from about 9 to about 18×10⁻⁶.

In another embodiment of the present invention, the concentration of Gais greater than 10 wt. %, and the concentration of B is from 0.15 to0.55 wt. %.

In still yet another embodiment, the concentration of Ga is from 10 to11.5 wt. %, the concentration of B is from 0.15 to 0.55 wt. %, theconcentration of Co is at least 37 wt. %, and the concentration of Cr isfrom 22 to 25 wt. %.

In still yet another such embodiment, the alloy composition is selectedfrom the group consisting of Co₄₀Cr_(24.35)Ru₂₅Ga_(10.5)B_(0.15),Co₄₀Cr_(23.35)Ru₂₅Ga_(11.5)B_(0.15),Co₄₀Cr_(23.95)Ru₂₅Ga_(10.5)B_(0.55),Co_(37.5)Cr_(22.95)Ru₂₅Ga_(11.5)B_(0.35), andCo₄₀Cr_(23.5)Ru₂₅Ga₁₁B_(0.5). The suffixes in these alloys representweight % of the elements in the alloys and not the atomic fractions.

In still yet another embodiment of the present invention, theconcentration of Ga is from 5 to 10 wt. %, the concentration of Co is atleast 35 wt. %, and the concentration of Cr is from 25 to 30 wt. %.

In still yet another embodiment, the alloy composition further comprisesup to 10 wt. % of an additive selected from the group consisting of W,Ta, Nb, Re, Mo and V.

In another aspect, the invention is directed to a dental product formedusing the alloys described above.

In yet another aspect, the invention is directed to a method ofmanufacturing a dental product formed using the alloys described aboveand using a technique selected from casting, molding, milling or lasersintering.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be more fully understood with reference to thefollowing figures and data graphs, which are presented as exemplaryembodiments of the invention and should not be construed as a completerecitation of the scope of the invention, wherein:

FIG. 1 provides a data graph showing the magnetic properties of anexemplary alloy in accordance with an embodiment of the invention;

FIG. 2 provides a data graph showing the magnetic properties of otherexemplary alloys in accordance with an embodiment of the invention;

FIG. 3 provides a data graph showing the magnetic properties of otherexemplary alloys in accordance with an embodiment of the invention; and

FIG. 4 provides a data graph showing the magnetic properties of otherexemplary alloys in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

A noble alloy (as defined by the American Dental Association) isconsidered to be one with at least 25 wt. % noble metal content, thenoble metals consisting of ruthenium, platinum, palladium, iridium,osmium, rhodium and gold. The alloy provided herein is noble, but isconsidered to be a cobalt-chromium based alloy since a high proportionof these base metals are in the alloy. It should be noted that unlessotherwise indicated all percentages herein are by weight.

The choice of ruthenium as a major additive has both metallurgical andeconomic benefits. For example, consider the approximate price/troyounce of gold and the platinum group metals as of December 2011:

Rhodium $1500 Platinum $1430 Gold $1600 Iridium $1050 Ruthenium $120Palladium $660Ruthenium is one of the lower cost metals relative to the other platinumgroup metals so there is an economic advantage to maximize the contentof ruthenium in place of gold and the other platinum group elements.

From a metallurgical perspective, ruthenium may substitute for othermaterials in cobalt, nickel and iron based alloys, such as for examplemolybdenum, tungsten, and, to a certain extent, chromium. Ruthenium actsas an alloy strengthener, is a thermal expansion adjuster for the alloys(to better match thermal expansion of dental porcelains), and reducesthe alloy's oxidation rate. Both ruthenium and chromium protect thealloy from corrosion and oxidation. The ruthenium enobles the alloy, dueto its non-reactive nature as opposed to the chromium that forms anoxide to protect the alloy from adverse reactions.

As discussed in the background, alloys incorporating elevated rutheniumconcentrations have been proposed in the past, such as, for example,U.S. Pat. No. 7,794,652, which describes a family of highly processablecobalt-chromium based ruthenium containing noble dental alloys. Whilethis patent focuses on maximizing the processability of these rutheniumcontaining cobalt-chromium alloys, no guidance is provided on how toensure that the alloys are not strongly-ferromagnetic. Table 1, below,provides a number of exemplary alloys meeting the requirements of theprior art that were found to have strong magnetic properties.

TABLE 1 Prior Art Co—Cr—Ru Alloys Alloy No. Formulation PA1Co40Cr25Ru25Ga10 PA2 Co37Cr25Ru25Ga13 PA3 Co38Cr25Ru25Ga12 PA4Co39Cr25Ru25Ga11

The current invention addresses the issue of minimizing the magneticproperties of ruthenium-containing cobalt-chromium alloys by carefullybalancing the concentrations of the base metals and through thejudicious use of select additives. It should be understood that thoughtruly non-magnetic, or paramagnetic alloys are preferred, in thefollowing description of this invention the term “non-magnetic alloy”refers to an alloy that is either paramagnetic or only weaklyferromagnetic, as shown in the attached data graphs.

The current invention is based upon the discovery that by carefullybalancing the relative proportions of cobalt, gallium and modifiers, itis possible to control the magnetic properties of ruthenium containingnoble cobalt chromium alloys and obtain processable alloys withnon-magnetic properties. The challenge to the metallurgist in composingsuch an alloy is in finding the balance between processability on theone hand and non-magnetism on the other. As described above in theBackground, previously it was thought that ruthenium containingcobalt-chromium alloys required a minimum concentration of gallium andcobalt to ensure that the processing characteristics of the alloys (suchas liquidus temperature) would be such as to allow them to be used inthe construction of dental appliances. However, it has now beendiscovered that when such alloys have a gallium content above about 10wt. % they may exhibit strong ferromagnetism upon slow cooling. Asdiscussed above, such strong ferromagnetism is an undesirable featurefor dental prostheses and appliances. Reducing the gallium content below10 wt. % eliminates this problem, but also lowers the thermal expansioncoefficient of the alloy. This may restrict the alloy's thermalcompatibility with some popular dental porcelain brands.

The alloys of the current invention address both factors—processabilityand magnetic properties—by judiciously manipulating the content ofcobalt, chromium, gallium, and certain additives. In particular, thereare two relevant compositional regimes for such ruthenium containingcobalt-chromium alloys: high gallium content alloys (greater than 10 wt.%); and low gallium content alloys (from 5 to 10 wt. % gallium). In thehigh gallium content alloys, it is necessary to include boron andcarefully control the content of cobalt in the alloy to ensure that thealloy retains its non-magnetic properties. In the low gallium alloys,the cobalt content may be reduced and boron eliminated, but in turn itis important to monitor the ratio of cobalt to gallium, and, in somealloys to include sufficient concentrations of certain specificadditives to ensure that the processability of these alloys ismaintained.

More particularly, alloys within the scope of this invention comprise:

-   -   at least 25 wt. % of ruthenium with only minor substitutions of        the other noble alloys—platinum, palladium, iridium, osmium,        rhodium and gold;    -   between 15-35 wt. % chromium;    -   from above 30 to 50 wt. % cobalt;    -   at least 5 wt. % gallium;    -   wherein where the concentration of Ga is from 5 to 10 wt. %,        preferably a ratio of Co to Ga of at least 4 to 1, and the alloy        further contains up to 5 wt. % of at least one modifier selected        from the group consisting Ge, Fe, B, In, Sn and Re where the        concentration of the modifier is selected such that the liquidus        temperature of the alloy is below 1600 C.°;    -   wherein where the concentration of Ga is greater than 10 wt. %,        the concentration of Co is at least 35 wt. %, the concentration        of Cr is less than 25 wt. %, and the alloy further contains B in        a concentration of up to 1 wt. %; and    -   wherein where the concentration of Ru is greater than 25 wt. %        then the Co to Ga ratio is less than 4 to 1.

Low Gallium Content Non-Magnetic Alloys

In some embodiments of the invention, the ruthenium containingcobalt-chromium dental alloy has a gallium content of between 5 and 10wt. %. In such embodiments, the alloy is a cobalt-chromium based alloycomprising at least 25 wt. % ruthenium; a sufficient amount of amodifier selected from Ge, Fe, B, In, Sn and Re to ensure the materialis sufficiently processable; chromium in the range of 15 to 35 wt. %,and preferably 25 to 35 wt. % and more preferably at least 30 wt. %cobalt. Preferably the ratio of cobalt to gallium is greater than 4 to1.

As discussed above, in some of these embodiments of the invention theaddition of a sufficient amount of the modifier's selected from thegroup of Ge, Fe, B, In, Sn and Re is necessary to obtain thermalexpansion properties suitable for the construction of dental appliances.In particular, the combination of high noble content and low galliumconcentration in alloys of this type can make it difficult for thealloys to be melted and shaped in the absence of very high temperatures.The addition of appropriate additives in accordance with the presentinvention lowers the melting temperature of the alloys so that they canbe melted with a natural gas- or propane-oxygen torch commonly used indental laboratories. Accordingly, in such embodiments sufficientmodifier is added to reduce the liquidus temperature sufficiently low toallow for the use of inductive heating to shape the material (less than1600 C.°), and preferably below 1450 C.°.

Accordingly, in these embodiments of the invention (between 5 and 10 wt.%, gallium), the total amount of such additives is at least 5 wt. %, andpreferably between 5 to 15 wt. %, with least 5 wt. % of the additivebeing gallium. In such alloys, as discussed, other substitutions may bemade and other additives may be included in amounts sufficient to lowerthe liquidus temperature preferably below at least 1600 C.°. Examples ofsuch substitutions and/or modifier additions include increasing theruthenium content in place of cobalt, or adding one of the modifierslisted from the group of Ge, Fe, B, In, Sn and Re as a substitute inplace of or in addition to gallium to ensure a suitable thermalexpansion coefficient.

Table 2, below, provides a listing of non-magneticchromium-cobalt-ruthenium-gallium alloys according to the inventionhaving between 5 and 10 wt. % gallium, and preferably with cobalt togallium ratios of greater than 4 to 1, that also demonstrate a liquidustemperature sufficiently low to ensure that the material is workable indental applications (less than 1600 C.°, and preferably less than 1450C.°). As is shown, a lower thermal expansion may be obtained by thejudicious use of the additives listed. In particular, as shown in Table1, by adding additives such as rhenium, germanium, iron or boron (Alloys17 to 27, Table 2 below). (The magnetic behavior of alloy 22 is shown asan example of the non-magnetic behavior of this group of compositions inFIG. 1.) The linear relationship between B and H in the data plotdemonstrates that the material has no magnetic response. The suffixesrepresent weight % of the elements in the alloys and not atomicfraction.

TABLE 2 Low Gallium Content Non-Magnetic Alloys Alloy No. Formulation 1Co50Cr15Ru25Ga10 2 Co40Cr20Ru30Ga10 3 Co41Cr25Ru25Ga9 4 Co42Cr25Ru25Ga85 Co41Cr26Ru25Ga8 6 Co39Cr28Ru25Ga8 7 Co37Cr30Ru25Ga8 8Co40Cr27.5Ru25Ga7.5 9 Co43Cr25Ru25Ga7 10 Co42Cr26Ru25Ga7 11Co40Cr28Ru25Ga7 12 Co38Cr30Ru25Ga7 13 Co42.5Cr26Ru25Ga6.5 14Co43Cr26Ru25Ga6 15 Co45Cr25Ru25Ga5 16 Co40Cr30Ru25Ga5 17Co40Cr25Ru25Ga5Re5 18 Co40Cr24.5Ru25Ga10B0.5 19 Co40Cr25.5Ru25Ga9B0.5 20Co40Cr26.5Ru25Ga8B0.5 21 Co40Cr27Ru25Ga7.5B0.5 22 Co37.5Cr30Ru25Ga7B0.523 Co40Cr29.5Ru25Ga5B0.5 24 Co44.75Cr25Ru25Ga5B0.25 25Co41Cr25Ru25Ga7Fe2 26 Co41Cr25Ru25Ga8Ge1 27 Co40Cr28Ru25Ga6.5Ge0.5

To demonstrate the criticality of the compositional limitations, otherexperiments were conducted to show the loss of non-magnetic propertiesif these compositional limitations are violated. As discussed withregard to Tables 1 and 2, above, the importance of the cobalt andgallium ratio was demonstrated by studying the prior art alloys,however, it was also discovered that there are important lower (30 wt.%) and upper (50 wt. %) limits to the amount of cobalt in the materialand a lower limit on the amount of gallium (greater than 5 wt. %) in thealloy, as shown in alloys 28 to 34, below, all of which showed stronglyferromagnetic properties during testing.

TABLE 3 Magnetic Co—Cr—Ru Alloys 28 Co51Cr15Ru25Ga9 29 Co55Cr15Ru25Ga530 Co50Cr20Ru25Ga5 31 Co60Cr15Ru25 32 Co55Cr20Ru25 33 Co42.5Cr30Ru25B0.534 Co30Cr25Ru25Ga10Fe10

High Gallium Content Non-Magnetic Alloys

As discussed above, in other embodiments of the invention, rutheniumcontaining cobalt-chromium alloys with high gallium concentrations (inexcess of 10 wt. %) that show low ferromagnetism may be obtained. As canbe appreciated with reference to FIGS. 2 to 4, by adding boron, and byjudiciously controlling the relative concentrations of cobalt, it ispossible to obtain compositions that are either paramagnetic, or thatshow only weak or no ferromagnetism.

FIG. 2 provides data in connection with a range of alloys that weretested showing a full range of magnetic behavior—from stronglyferromagnetic to paramagnetic. FIG. 3 shows those alloys (those with lowcobalt concentrations) that exhibited a strong magnetic response (notethe typical curve in these data plots, and for a few samples, ahysteresis effect that are indicative of a strong ferromagneticbehavior.) However, note that as the cobalt concentration increases andthe boron is added the compositions lose their ferromagnetic behaviorand become more paramagnetic (i.e. the relation between B and H in thedata plots is linear). Finally, FIG. 4 shows those alloys, according tothe invention, that were weakly ferromagnetic or paramagnetic. (Thechange in the y-axis scale should be noted.) These alloys are ofparticular value since the materials also exhibit the required thermalproperties to bond to popular porcelains, yet show little or noferromagnetic behavior.

Of importance in these embodiments of the invention is the inclusion ofsufficient cobalt, the judicious use of boron, and the careful titrationof chromium to render the alloy non-magnetic. With decreasing gallium,as shown in the embodiments above, it is possible to decrease the cobaltconcentration and increase the concentration of chromium. As the galliumconcentration increases, however, it is necessary to add boron, decreasethe concentration of chromium and increase the concentration of cobalt.Thus, by adjusting the compositional contributions of chromium, cobaltand boron, the alloys of the invention can be made paramagnetic orferromagnetic, even at high gallium content, which has never before beendemonstrated.

Thus, in these embodiments, the alloys of the present invention includecobalt-chromium based alloys comprising at least 25 wt. % of ruthenium;greater than 10 wt. % gallium, and preferably from between 10.5 to 11.5wt. % gallium; a non-zero concentration of up to 1 wt. % boron, andpreferably from 0.15 to 0.55 wt. % boron; chromium in the range of 20 to25 wt. %, and preferably 22 to 25 wt. %; and a balance of Co, where thecobalt content is above 35 wt. %.

Table 4, below, provides a summary listing of thechromium-cobalt-ruthenium-gallium alloys studied. In these alloys,non-magnetic properties were obtained by the judicious use of boron andchromium. In particular, as shown in Table 2 by including a small amountof boron, and decreasing the chromium concentration, it is possible toobtain alloys with high gallium concentrations (greater than 10 wt. %)that consistently demonstrate non-magnetic properties. The suffixesrepresent weight % of the elements in the alloys and not atomicfractions.

TABLE 4 High Gallium Content Non-Magnetic Alloys Alloy No. FormulationMagnetic Property 35 Co35Cr29.35Ru25Ga10.5B0.15 Ferromagnetic 36Co40Cr23.5Ru25Ga11B0.15 Paramagnetic 37 Co40Cr24.35Ru25Ga10.5B0.15Paramagnetic 38 Co35Cr28.35Ru25Ga11.5B0.15 Ferromagnetic 39Co40Cr23.35Ru25Ga11.5B0.15 Paramagnetic 40 Co40Cr24Ru25Ga10.85B0.15Paramagnetic 41 Co37.5Cr22.95Ru25Ga11.5B0.35 Paramagnetic 42Co33.5Cr30Ru25Ga11B0.5 Ferromagnetic 43 Co40Cr23.5Ru25Ga11B0.5Paramagnetic 44 Co35Cr28.95Ru25Ga10.5B0.55 Ferromagnetic 45Co40Cr23.95Ru25Ga10.5B0.55 Paramagnetic 46 Co35Cr27.95Ru25Ga11.5B0.55Ferromagnetic 47 Co40Cr22.95Ru25Ga11.5B0.55 Ferromagnetic

General Compositional Considerations

It should be noted that in the above embodiments the amount of noblemetal in the alloy may be greater than 25 wt. %, up to as much as 45 wt.% (as shown in Table 5, below) and still maintain the non-magneticproperties described herein, but there is no economic advantage to usingthese higher concentrations of the costly material. In addition,although the alloys of the invention comprise at least 25 wt. %ruthenium, it will be understood that additions or substitutions ofother noble metals selected from the list of ruthenium, platinum,palladium, iridium, osmium, rhodium and gold may be made withoutfundamentally changing the nature of the material.

TABLE 5 High Ru Content Alloys 48 Co35Cr25Ru30Ga10 49 Co40Cr20Ru30Ga1050 Co25Cr20Ru40Ga15 51 Co25Cr20Ru45Ga10

In addition to the main components as described above, the alloys of thepresent invention may also contain trace concentrations of otheradditives to improve specific properties. For example, up to about 10%of molybdenum, silicon, vanadium, tungsten, niobium, tantalum and/or theRare Earths (or appropriate combinations of these elements) to furtheradjust coefficient of thermal expansion (CTE), to enhance the castingcharacteristics of the alloy and for grain refinement. Finer graincastings are more readily ground to a smooth finish suitable forcovering with dental ceramics. However, it should be understood thatthese additives are not essential to the practice of the currentinvention.

It is appreciated that the above compositions are suitable for use withdental appliances, but are not to be considered exclusive. Those ofskill in the art will be aware that some of the materials can besubstituted or additional materials may be added without altering thekey properties of the alloys of the current invention. For example,small concentrations (less than 5 wt. %) of other materials may also beadded or be found in the alloy as impurities without affecting theproperties of the overall composition, some of these include, forexample, Al, Si, V, W, Ta, Nb, Re, Mo and the Rare Earths.

Although the above description has focused on a range of compositionsfor alloys of the current invention suitable for use in, for example,dental applications, the invention is also directed to dental productsmade from the alloys and to methods of manufacturing dental productsfrom the alloys. In general, such methods will include the steps ofproviding an alloy having a composition in accordance with the abovedescription and then shaping the dental product with that alloy usingany suitable means. In this regard, the alloys of the present inventionallow for the use of a number of conventional shaping techniques, suchas, casting and molding. Moreover, the alloys of the invention alsoallow for the use of more recent advances in shaping technologies, suchas, for example, CAD/CAM milling and selective laser sintering. Itshould be understood that any of these techniques or a combinationthereof may be used with the alloys of the present invention.

Specifically, despite their high hardness value, the alloys may beground using traditional dental laboratory grinding media making themespecially suited for use with newer CAD/CAM and powder metallurgicalapplications where no casting is required. In one such technique,substrates or final restorations can be milled from blocks made fromthese alloys. As powders, these alloys can be used either to createthree dimensional performs utilizing appropriate binders and then besintered, or can be directly sintered/melted such as for example, with alaser, to create substrate or final restoratives. Exemplary disclosuresof such processes can be found, for example, in U.S. Pat. Nos. 7,084,370and 6,994,549, the disclosures of which are incorporated herein byreference. It should be understood that while some prior art lasersintering techniques specify a specific range of useable alloyparticulate sizes, the alloys of the current invention are contemplatedfor use in laser sintering techniques over all possible particulate sizeranges.

DOCTRINE OF EQUIVALENTS

Those skilled in the art will appreciate that the foregoing examples anddescriptions of various preferred embodiments of the present inventionare merely illustrative of the invention as a whole, and that variationsin the relative composition of the various components of the presentinvention may be made within the spirit and scope of the invention. Forexample, it will be clear to one skilled in the art that typicalimpurities and/or additives may be included in the compositionsdiscussed above that would not affect the improved properties of thealloys of the current invention nor render the alloys unsuitable fortheir intended purpose. Accordingly, the present invention is notlimited to the specific embodiments described herein but, rather, isdefined by the scope of the appended claims.

1. A dental alloy comprising: at least 25 wt. % of Ru; from 15 to 35 wt.% Cr; from 30 to 50 wt. % Co; and at least 5 wt. % Ga; wherein where theconcentration of Ga is from 5 to 10 wt. % the alloy further contains asufficient concentration up to 5 wt. % of at least one modifier selectedfrom the group consisting Ge, Fe, B, In, Sn and Re such that theliquidus temperature of the alloy is below 1600 C.°; wherein where theconcentration of Ga is greater than 10 wt. %, the concentration of Co isat least 35 wt. %, the concentration of Cr is less than 25 wt. %, andthe alloy further contains B in a concentration of up to 1 wt. %; andwherein the alloy is non-magnetic.
 2. The dental alloy of claim 1,wherein the concentration of Ga is between 5 and 10 wt. % and theconcentration of Ru is greater than 25 wt. % then the ratio of Co to Gais 4 to 1 or less.
 3. The dental alloy of claim 1, wherein theconcentration of Ga is between 5 and 10 wt. %, and wherein the alloyfurther contains at least 1 wt. % Re.
 4. The dental alloy of claim 1,wherein the concentration of Ga is between 5 and 10 wt. %, and whereinthe total concentration of Ga and Re is at least 10 wt. %.
 5. The dentalalloy of claim 1, wherein the alloy further comprises less than 5 wt. %of at least one trace additive selected from the group consisting ofcopper, nickel and iron.
 6. The dental alloy of claim 1, wherein thealloy has a composition selected from the group consisting ofCo₄₀Cr_(27.5)Ru₂₅Ga_(7.5), Co₃₈Cr₃₀Ru₂₅Ga₇, Co₄₁Cr₂₅Ru₂₅Ga₈Ge₁,Co₃₅Cr₂₅Ru₃₀Ga₁₀, Co₄₀Cr₂₅Ru₂₅Ga₅Re₅, and Co_(37.5)Cr₃₀Ru₂₅Ga₇B_(0.5).7. The dental alloy of claim 1, wherein the alloy has a thermalexpansion coefficient within the range of from about 9 to about 18×10⁻⁶.8. The dental alloy of claim 1, wherein the concentration of Ga isgreater than 10 wt. %, and wherein the concentration of B is from 0.15to 0.55 wt. %.
 9. The dental alloy of claim 1, wherein the concentrationof Ga is between 10 and 11.5 wt. %, the concentration of B is between0.15 and 0.55 wt. %, the concentration of Co is at least 37 wt. %, andthe concentration of Cr is between 22 and 25 wt. %.
 10. The dental alloyof claim 1, wherein the alloy has a composition selected from the groupconsisting of Co₄₀Cr_(24.35)Ru₂₅Ga_(10.5)B_(0.15),Co₄₀Cr_(23.35)Ru₂₅Ga_(11.5)B_(0.15),Co₄₀Cr_(23.95)Ru₂₅Ga_(10.5)B_(0.55),Co_(37.5)Cr_(22.95)Ru₂₅Ga_(11.5)B_(0.35), andCo₄₀Cr_(23.5)Ru₂₅Ga₁₁B_(0.5).
 11. The dental alloy of claim 1, whereinthe concentration of Ga is between 5 and 10 wt. %, the concentration ofCo is at least 35 wt. %, and the concentration of Cr is between 25 and30 wt. %.
 12. The dental alloy of claim 1, wherein the alloy furthercomprises up to 10 wt. % of an additive selected from the groupconsisting of Si, W, Ta, Nb, Re, Mo and V.
 13. A dental alloycomprising: at least 25 wt. % of Ru; from 15 to 35 wt. % Cr; from 30 to50 wt. % Co; from 5 to 10 wt. % Ga; further contains a sufficientconcentration of up to 5 wt. % of at least one modifier selected fromthe group consisting Ge, Fe, B, In, Sn and Re such that the liquidustemperature of the alloy is below 1600 C.°; wherein the ratio of Co toGa is greater than 4 to 1; and wherein the alloy is non-magnetic.
 14. Adental alloy comprising: at least 25 wt. % of Ru; from 15 to 25 wt. %Cr; from 35 to 50 wt. % Co; at least 10 wt. % Ga; wherein the alloyfurther contains B in a concentration of up to 1 wt. %; and wherein thealloy is non-magnetic.
 15. A dental product comprising: a metallic bodyfor dental application, said body being formed of a dental alloycomprising: at least 25 wt. % of Ru; from 15 to 35 wt. % Cr; from 30 to50 wt. % Co; and at least 5 wt. % Ga; wherein where the concentration ofGa is from 5 to 10 wt. % the alloy further contains a sufficientconcentration up to 5 wt. % of at least one modifier selected from thegroup consisting Ge, Fe, B, In, Sn and Re such that the liquidustemperature of the alloy is below 1600 C.°; wherein where theconcentration of Ga is greater than 10 wt. %, the concentration of Co isat least 35 wt. %, the concentration of Cr is less than 25 wt. %, andthe alloy further contains B in a concentration of up to 1 wt. %; andwherein the alloy is non-magnetic.
 16. The dental product of claim 15,wherein the concentration of Ga is between 5 and 10 wt. % and theconcentration of Ru is greater than 25 wt. % then the ratio of Co to Gais 4 to 1 or less.
 17. The dental product of claim 16, wherein theconcentration of Ga is between 5 and 10 wt. %, and wherein the alloyfurther contains at least 1 wt. % Re.
 18. The dental product of claim15, wherein the concentration of Ga is between 5 and 10 wt. % andwherein the total concentration of Ga and Re is at least 10 wt. %. 19.The dental product of claim 15, wherein the alloy further comprises lessthan 5 wt. % of at least one trace additive selected from the groupconsisting of copper, nickel and iron.
 20. The dental product of claim15, wherein the alloy has a composition selected from the groupconsisting of Co₄₀Cr_(27.5)Ru₂₅Ga_(7.5), Co₃₈Cr₃₀Ru₂₅Ga₇,Co₄₁Cr₂₅Ru₂₅Ga₈Ge₁, Co₃₅Cr₂₅Ru₃₀Ga₁₀, Co₄₀Cr₂₅Ru₂₅Ga₅Re₅, andCo_(37.5)Cr₃₀Ru₂₅Ga₇B_(0.5).
 21. The dental product of claim 15, whereinthe alloy has a thermal expansion coefficient within the range of fromabout 9 to about 18×10⁻⁶.
 22. The dental product of claim 15, whereinthe concentration of Ga is greater than 10 wt. %, and wherein theconcentration of B is between 0.15 and 0.55 wt. %.
 23. The dentalproduct of claim 15, wherein the concentration of Ga is between 10 and11.5 wt. %, the concentration of B is between 0.15 and 0.55 wt. %, theconcentration of Co is at least 37 wt. %, and the concentration of Cr isbetween 22 and 25 wt. %.
 24. The dental product of claim 15, wherein thealloy further comprises up to 10 wt. % of an additive selected from thegroup consisting of Si, W, Ta, Nb, Re, Mo and V.
 25. The dental productof claim 15, wherein the alloy has a composition selected from the groupconsisting of Co₄₀Cr_(24.35)Ru₂₅Ga_(10.5)B_(0.15),Co₄₀Cr_(23.35)Ru₂₅Ga_(11.5)B_(0.15),Co₄₀Cr_(23.95)Ru₂₅Ga_(10.5)B_(0.55),Co_(37.5)Cr_(22.95)Ru₂₅Ga_(11.5)B_(0.35), andCo₄₀Cr_(23.5)Ru₂₅Ga₁₁B_(0.5).
 26. The dental product of claim 15,wherein the concentration of Ga is between 5 and 10 wt. %, theconcentration of Co is at least 35 wt. %, and the concentration of Cr isbetween 25 and 30 wt. %.
 27. The dental product of claim 15, whereinwhere the concentration of Ga is from 5 to 10 wt. % then the ratio of Coto Ga is greater than 4 to 1.